Patent GB-191303344-A (GB)
Title: Improved Circuit Arrangements for Junction Lines at Automatic and Semi-automatic Telephone Exchanges.
Filed: 1913-02-08
Granted: 1914-03-09
Abstract: 3344. Siemens & Halske Akt.-Ges. Feb. 10, 1912, [Convention date.] Automatic and semi-automatic exchange systems; metering systems. - In systems using junction lines, having only two leads, between exchanges or between groups of lines in the same exchange, and in which selectors having more than two leads, are used, the lead or leads not included in the speaking circuit are temporarily connected to the junction line so as to repeat from one group or exchange to the next such operations as testing the junction lines, registering the call, &c. which are not effected over the speaking leads. Two methods of carrying out the invention are described, that shown in Fig. 1 having the third or c-leads normally connected directly to the junction line b, while in that shown in Fig. 2, the test potential on the outgoing junction is controlled by a relay V normally energized over the junction lead a. First system, Fig. 1. A selector repeater, represented by its test relay P, and described in Specification 2672/12, is shown connected to the junction a, b, terminating in leads 26, 27, 28 of a group selector. The test lead c is normally connected over contacts 6, 4, junction b, relay C, and test lead c<1> to battery, so that when the test wiper 32 finds an idle junction, the relay P energizes in series with the relay C, which by closing. contact 10 connects the relay A in series with a slow-acting relay E, which (1) opens at contact 6 the connexion between the test lead c and the junction b, and (2) by closing contact 7 energizes a self-locking relay F, which maintains the circuit of the test relay P, and extends the wipers 23, 24 to the junction leads a, b. After the leads b, c have been disconnected, the relay C remains energized in series with the relay B at first over contact 15 and then over contact 13. When the relay A is de-energized by the disconnexion of the relay E, the closure of contact 17 energizes a low-resistance relay D, which by closing contact 21 withdraws so much current from the relays B, C, that they de-energize. The closure of contacts 19, 20 extends the junction a, b to the lead 26, 27, the relays A, B being connected in bridge across the junction circuit. During a conversation, the relays P, F, D alone are energized. At the end of a conversation, the selector repeater is released in known manner, thus opening the circuit over the test lead c so as to de-energize the relay F, which connects the relay E to the lead a and relay A, which in turn short-circuits the relay D at contact 16, thus restoring the junction line to its initial condition. The relay F is provided with an additional winding 34, which keeps the relay F energized so as to mark the junction line busy until the apparatus at the incoming end of the junction has recovered its normal condition. Second system, Fig. 2. A calling selector W represented by its test relay T1 and meter M is shown connected to the junction line a, b, terminating at its outgoing end in a repeater U and at its incoming end in a preliminary selector VW, adapted to find an idle group selector GW. The test lead c is normally grounded through a relay C and a contact 57 of a relay V, which is energized over contacts 74, 53, relay Z, junction lead a, contacts 61, 64, winding r2 of the call relay of the preliminary selector contact G, (which can be depressed to lock the junction out of action) and one or more of the contacts 69, 70, 71 controlled by the selectors accessible from the preliminary selector VW. If the junction a, b is engaged this circuit is open at contact 61, and if all the group selectors accessible from it are in use the contacts 69, 70, 71 are all open, so that in either case the relay V is not energized and the contact 57 is open. The circuit including the relays V, Z, R is normally closed, but the resistance of the relay V prevents relays Z and R from being affected. When a selector W makes connexion with the junction a, b, the relay T1 energizes in series with the relay C, which locks up over contacts 48. The closure of contacts 59, 51 by the relays A, B completes a circuit for the call relay R of the preliminary selector VW, which rotates until the cut-off relay T2 energizes in series with the relay C, of an idle group selector, and extends the junction a, b to the relays A1, B1, which are energized over the contacts 51, 59 of the repeater U. During the transmission of the selecting-impulses the relays B, X are energized, and the relay A is intermittently de-energized. The closing of contacts 49, 55 bv the relays B, X earths both junction lines, the circuit over the a lead being intermittently broken at contact 59 by the relay A, so that the relays A1, B1, X1 operate the group selector GW in known manner. Release and metering calls. The release of the connector bv either subscriber connects battery potential, as described in Specification 6654/10, to the speaking lead 44, and if, or when, the relay B, is de-energized by the calling subscriber hanging up, the metering relay ZR is energized over contacts 72, 67 and the lead 44, and, by closing contact 66, increases the current in the test lead c<1> sufficiently to energize a slow-acting relay ZL. When the current through the relay ZR ceases, the circuit over the test lead c' is interrupted, and the relay T2 releases its armature; and since the relay ZL releases slowly, a current impulse passes over contacts 65, 61, junction a, contact 50, relay Z, and contact 53 to earth. The relay Z closes contact 58, thus increasing the current in the test lead c sufficiently to operate the meter M. In order to prevent improper operation of the meter when the calling subscriber hangs up, due to the relay B closing contact 52 before the relay Z has opened contact 58, the quick de-energizing of the relay Z is ensured by arranging that the energy stored in the relay A, and its condenser shall be discharged over the junction a through the relay Z in the direction necessary to neutralize the current flowing through the relay during a conversation.